Crude oil and hydrocarbon fractions thereof are known to contain organic acids, e.g., naphthenic acids that cause corrosion problems in transportation pipelines and in oil refinery equipment used to process the oil.
In a conventional de-acidification process, an acidic oil, i.e., a hydrocarbon containing a naphthenic acid, is mixed with an alkali such as sodium hydroxide or potassium hydroxide and water. The mixing produces an emulsion which may be separated into an aqueous phase and an oil phase with addition of a de-emulsifier. The neutralization reaction produces an alkali metal salt in the aqueous phase which is removed from the resulting oil phase having a reduced acid content. The acidic oil may be a whole or full range crude that is suitable as feed to a crude distillation zone or an acidic hydrocarbon fraction produced by the crude distillation zone or other process zones in a refinery.
PCT application PCT/GB2007/001985 published as WO 2007/138307 A2 discloses a sulfur-containing acid removal process for deacidifying a crude oil and/or crude oil distillate containing sulfur-containing acids comprising the steps of: (a) contacting the crude oil and/or crude oil distillate containing sulfur-containing acids with a basic ionic liquid having a melting point of below 150° C., and extracting at least a portion of the sulfur-containing acids into the basic ionic liquid as an extract phase; and (b) separating a crude oil and/or crude oil distillate phase which is reduced in acidity from the basic ionic liquid phase.
There remains a need in the art for improved or alternate processes that reduce the acid content of crude oil and acidic hydrocarbon fractions.